Two hormonally-regulated developmental systems are being investigated. Dictyostelium development is dependent upon signal transduction mediated by cell surface, cAMP receptor/G protein linkages. Here secreted cAMP acts extracellularly as a chemoattractant and primary signal to control cell motility, aggregation (multicellularity), cytodifferentiation, pattern formation and cell-type specific gene expression. We have previously isolated and disrupted 4 genes for distinct cAMP receptor subtypes, CARs 1, 2, 3 and 4. Analyses of CAR4-null cells indicate a role in cell differentiation and pattern formation. Differentiated cells localize to incorrect regions of the developing organisms. The promoters for CAR3 and CAR1 (early) expression have been dissected. We have identified short sequence regions within each that are required for their respective temporal, spatial and cAMP-regulated expression. The sequences exhibit specific binding to proteins isolated from nuclei at appropriate developmental stages. The zZIP1 protein of Dictysotelium possesses a leucine zipper and zinc fingers and is a presumed transcription factor. Dictyostelium carrying a disruption of the zZIP1 gene appear to have lost a subset of differentiated cells, the prestalk O cells, suggesting that zZIP1 is required for their differentiation or cell-type specific gene expression. The spiA gene appears to be a marker for terminal differentiation. We have used it to predict a gradient for spore differentiation and to examine the linkage between activation of cAMP dependent-protein kinase (PKA) and sporulation. We have also identified promoter sequences within spiA that are responsive to PKA activation. The mammalian adipocyte is also regulated by hormone response. 3T3-L1 adipoblasts will differentiate into adipocytes when cultured with dexamethasone and insulin. During differentiation a variety of adipocyte markers become specifically expressed. One of these is perilipin. Previously we had shown that perilipin is an adipocyte- specific protein located at the periphery of lipid droplets and had isolated cDNAs for perilipin. We now show that perlipin plays a significant role in the function of the adipocyte. Overexpression of perilipin appears to accelerate the rate of differentiation, whereas, antisense constructs used to block expression of perilipin appears to inhibit differentiation.